Wood chip mulch is an attractive ground cover that enhances the health of your soil and the plants you grow.
For many gardeners, carpeting the landscape with organic mulches becomes an indispensable part of building new planting beds and replenishing the older ones. The moisture conservation and weed suppression benefits alone make mulching well worth the effort.
If you want to keep a low-maintenance garden, you really must mulch.
7 Reasons Wood Chips Make Great Mulch
Organic mulches mimic the constant shedding of sticks, branches, bark, and leaves that occurs in forest ecosystems. Perennial plants evolved steeped in layers upon layers of plant litter and have adapted to all the benefits that come with nature’s mulching.
Arborist wood chips are the closest to the natural mulching in forests and woodlands. Derived from the fresh branches and brush from trimmed trees run through a wood chipper, the wood chip pieces are large and chunky – ranging in size from 2 to 4 inches long and an inch or two in diameter.
Wood chips make excellent mulch. It has all the classic benefits you can expect from a landscape mulch, plus a few traits that are unique only to wood chips:
Suppress weeds
Like any good mulch, wood chips spread at a depth of at least 4 inches will control most annual weeds. It prevents seeds from germinating and stalls the spreading growth of perennial weeds by blocking sunlight from reaching them. Aside from having to do a whole lot less weeding, mulches help your desired plants grow better because they are not directly competing against weeds for nutrients, water, and space.
Retain moisture
Without a blanket of mulch to shade the soil and hold in moisture, soil loses water quickly through evaporation into the atmosphere. To keep moisture in and maximize water savings, use mulches that have larger particles and a coarser texture than the soil below. Finer mulches like compost, leaf mold, or sawdust have a tendency to pull water up from the soil. Using chunkier mulches with a particle size of 1 inch or greater is better for keeping moisture in the ground, meaning fewer irrigation trips around the garden.
Enrich the soil
As fresh organic mulches decompose over time, they dramatically impact soil health. Gardens mulched with woody materials will, over the next season or two, have higher nutrient levels, enhanced moisture-holding capacity, increased soil porosity, and improved overall soil structure. Plants grown in them have better rooting and root development.
Encourages soil microflora
Fresh and undecomposed wood chips are best for providing a carbon food source for soil microbes and fungi – especially mycorrhizal fungi – that break it down into nutrients that plants can absorb. The uptick in soil microorganism activity keeps the earth a healthy place to grow by suppressing root disease and soil pathogens.
Regulate soil temperature
Mulch is a natural insulator that helps keep the soil cooler in summer and warmer in winter. It shades the ground and significantly slows moisture loss in hot weather, protecting plants from drying and heat stress.
In colder periods, it stabilizes soil temperatures to maintain more consistent conditions that are slower to change. It insulates roots and soil microbes from wide temperature swings from day to night, extending your growing season deeper into fall.
Controls erosion
Soil left exposed to the elements is prone to erosion, which is accelerated by rain, wind, and slope. Erosion degrades soil health by wearing away the fertile upper layers of soil and can lead to plant root damage through loss of nutrients. Mulch applied thickly shields the soil from direct hits from intense rain or hail, holds it in place in the wind, and keeps sloping terrain from washing away.
Long lasting
Although there are many types of mulching materials, wood chips are one of the longest-lasting organic mulches. Unlike finely shredded mulch, which breaks down fairly quickly and often needs annual replenishment, arborist wood chips are larger, chunkier, and slower to decompose. The general rule is that 1 inch of wood chips will last a year. Apply 4 inches or more, and you shouldn’t need to mulch again for another 4+ years.
Are There Any Risks Using Wood Chip Mulch?
There are numerous claims swirling around the internet about the negative impacts of using wood chip mulch in the garden and landscape. But for the most part, these concerns are overblown or completely unfounded:
Fresh wood chips don’t tie up nitrogen in the soil.
Although wood chips are mostly carbon and require nitrogen to decompose, there’s no evidence that wood chip mulch will cause nitrogen deficiencies in your plants. The top inch of soil might lack nitrogen due to the presence of wood chips, so don’t mulch around delicate seedlings until they are better established.
Your wood chip pile won’t spontaneously combust.
For wood chips to get hot enough to catch fire, piles would need to be enormous – greater than 60 feet tall, 300 feet wide, and 500 feet long.
Wood chips aren’t particularly attractive to termites.
These social insects are just as frequently spotted under pea gravel and below uncovered soil. Still, it’s best to pull mulch away from your home’s foundation, siding, and windowsills.
Wood chips from allelopathic species – like Black Walnut – don’t harm plants.
Some allelopathic chemicals remain in the wood after it’s chipped, but they are rapidly broken down in the environment. Again, avoid using wood chip mulch around fragile seedlings.
Wood chips containing pine bark and needles won’t acidify your soil.
It would take many years, even decades, of mulching for the mulch to have any impact on soil pH.
The risk of wood chips spreading disease is low.
Most tree diseases aren’t spread through wood chip mulch, but transmission is possible. As long as wood chips sit on top of the soil – and aren’t worked into the soil – it is unlikely that pathogens will infect healthy tree roots.
The mulching process destroys most pests and weeds.
Wood, bark, and leaves that go through a wood chipper will eliminate the majority of tree pests and invasive weeds that could be present.
There is no need to let a fresh pile of wood chips age for a year.
Generally, it is safe to use fresh wood chips in your garden when you locate your mulch from trusted sources. If you are worried about introducing invasives to your yard through wood chips, you can age – or compost – your wood chip pile. Let the heap sit awhile and it will heat up and destroy any pests or weeds. The caveat is composted mulch will have a finer particle size and won’t be as nutritious as wood chips used fresh.
How to Get Free Wood Chip Mulch
To build out vast ornamental beds or replenish existing gardens, you’re going to need a lot of mulch to attain the minimum 4 inches in depth. A few bags of shredded mulch from the store aren’t going to go very far. And at $3 or $4 per bag, the costs of mulching can add up quickly.
Good news is you can often find heaps of wood chip mulch for free when you know where to look:
1. Arborists
Arborists are certified tree experts who can assess the health of trees on your property. If necessary, they will remove dead wood and weak limbs now so they are not a huge problem later.
Whenever you need tree work done, it’s an excellent opportunity for free mulch. Instead of having the chopped down branches and smaller limbs hauled away, ask if you can have the brush chipped on-site and dumped in an out-of-the-way spot on the lawn.
Not only will this mulch be fresh, the wood chips will be from a known source that you can be certain carries no pests or pathogens.
Arborists come into contact with plenty of wood chips through the course of their tree work. So, even if you don’t need any hazardous trees that need trimming, reach out to arborists in your area to see if they have fresh mulch they need to dispose of.
(Our editor, Tracey, used to work for an arborist, and she confirms that if you call, most have a list and will happily wood chip mulch for free when they do work in your area.)
2. Utility Companies
Utility companies are responsible for maintaining residential power lines. As part of routine maintenance throughout the year – but especially after a big storm – utility or city crews are often seen out trimming trees, with a dump truck and wood chipper in tow.
If you spot a crew clearing branches in your neighborhood, ask if you can have the wood chips dumped on your property. Most will be more than happy to do it, since giving it away saves them from having to pay disposal fees.
Drive around your neighborhood a day or two after heavy storms, and you’re likely to come across a utility company cleanup crew. After a tornado went through her backyard this spring, our editor, Tracey, was able to get a free load of wood chip mulch roughly two times the size of her Subaru Outback!
3. Community Programs
If your town or landfill runs a green waste program, there’s a good chance they will have compost and mulch giveaways.
Yard waste – composed mainly of tree and shrub trimmings collected from a multitude of households – is brought back to the facility, chipped, and dumped into enormous piles. It’s free for the taking, and you can pick up as much or as little as you want.
Usually you will need to bring your own shovel and containers to the site – and have enough space in your vehicle to transport it to your home. If you only need a little mulch, use heavy-duty bags, plastic totes, or garbage cans. If you want more mulch, shoveling the wood chips directly into the back of a pickup truck or a trailer bed is a far more efficient way of gathering it.
4. ChipDrop
ChipDrop is a fantastic online service that connects local arborists with gardeners in need of wood chip mulch. Sign up for an account, put in a request, and you could have a free load of mulch delivered right to your home.
Using ChipDrop is a bit of a wildcard. You must be willing to accept an entire dump truck worth of wood chips (up to 20 cubic yards), but you may get as little as 4 yards or so. You might receive your mulch delivery the same day you request it or anywhere from 1 to 5 weeks later. Sometimes it takes longer, especially in winter or if ChipDrop isn’t very active in your area.
You also won’t have much warning when the wood chips are en route and it’s possible you won’t be home when the mulch is delivered. When putting in a request for wood chips, you have the option of uploading a photo of the site you wish to have the wood chips dumped. Place a flag, pylon, or some other marker on the spot so the arborists know exactly where to offload the chips.
How to Use Up a Huge Pile of Wood Chips
Even if you have a small yard, a large pile of wood chips can go quite quickly when you spare no bare spots of soil. Mulching to a depth of 4 inches or more can deplete a huge heap faster than you might think.
It never takes me very long to get through a pile of wood chips because I apply it absolutely everywhere. It goes into new and old ornamental beds, as well as every container, hanging basket, pot, and window box. I even add wood chips around established plants in my vegetable plot.
Beyond applying them to your annual and perennial beds, wood chips are perfect for creating attractive paths around your garden. Even when wet, they won’t stick to your feet.
Once I’ve mulched all I can possibly mulch, I use up any remaining wood chips in my compost as an all-natural source of carbon.
More Wood Chip Mulching Tips:
To get the most out of your mulch heaps, there are a few things to note before you use it in your gardens.
- For maximum soil enrichment and microbial activity, use fresh tree trimmings that contain both wood and leaves.
- For the best weed suppression, you can apply wood chips anywhere from 4 to 12 inches deep.
- For longevity, wood chip pieces should be larger than 1 inch in diameter.
- After you’ve mulched, periodically check moisture by pulling back the wood chips and sticking your finger in the soil.
- When irrigating mulched beds, water deeply to ensure moisture penetrates through the wood chips and reaches the soil.
- Pull mulch about 8 inches back from tree trunks to avoid collar rots.
- Although the risk of spreading pathogens, pests, or weeds in mulch is low, it’s always prudent to get your wood chips from reputable sources.
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